How fine particles on haematite mineral ultimately define the mineral surface charge and the overall floatability behaviour

Mineral floatability is strongly connected with mineral structure and composition. The complexity of mineral surfaces has meant that few attempts have been made to understand the effect of impurities(trace elements) on the flotation process. Zeta potential technique has been extensively used to evaluate the surface charge of mineral particles. Nevertheless, those measurements consider only anaverage of mineral particles surface charge. The presence of fine particles and inclusions covering a mineral may influence the local reagent adsorption process, which will ultimately be reflected in the subsequent global response of the mineral froth flotation efficiency. The current work assesses the iron oxide mineral, haematite (Fe2O3). Zeta potential and streaming potential techniques were used to determine the surface charge of fine and coarser particles of haematite. Further analysis was performed to determine the point of zero charge (PZC) of the mineral. In addition, adsorption isotherms of alkylammonium chloride reagents with different lengths of carbon chains were carried out. It was found haematite floatability depends strongly on the isoelectric point (IEP) value, which is affected by other mineral species present at the mineral surface. Haematite floatability became significant only at relatively high tetradecyl ammonium chloride collector concentrations (concentration greater than 4 10-4 M), which does not happen with other oxides such as quartz. Unlike quartz, haematite develops a low surface charge over a wide range of pH, disabling all long-range attractive interactions between the mineral and the collector. Therefore, hydrophobic chain interaction is probably the most likely mechanism acting to promote collector adsorption and enhance further floatability. Diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to suggest a possible mechanism to understand the sequence of collector adsorption and the effect of trace species on it

Study of divalent heavy metal ions adsorption by using radiata bark pine

Radiata bark pine has arisen as one of the possible heavy metals extracting agent from aqueous solutions. This innocuous treatment pathway, example of the so-called clean technology, has been studied for numerous authors nevertheless some issues, like global mechanism, are still not well described. This work is devoted to determine the effect of initial-normal heavy metal content present in radiata bark pine over its own ion extraction capability. Separate batch experiences at different conditions of both Cu(II) and Pb(II) adsorption were performed. Many authors have demonstrated that pulp density affect largely the bark pine extraction capability. In equilibrium conditions, the solid/liquid ratio itself defines the adsorption capacity independently of both heavy metal concentration and bark surface state. FTIR, PIXE and SEM analysis corroborated these facts and also proved the existence of different adsorption energy sites. Further kinetic analysis was performed to understand the different adsorption behavior of Cu(II) and Pb(II)

A foam film propagating in a confined geometry : analysis via the viscous froth model

A single film (typical of a film in a foam) moving in a confined geometry (i.e. confined between closely spaced top and bottom plates) is analysed via the viscous froth model. In the first instance the film is considered to be straight (as viewed from above the top plate) but is not flat. Instead it is curved (with a circular arc cross-section) in the direction across the confining plates. This curvature leads to a maximal possible steady propagation velocity for the film, which is characterised by the curved film meeting the top and bottom plates tangentially. Next the film is considered to propagate in a channel (i.e. between top and bottom plates and sidewalls, with the sidewall separation exceeding that of the top and bottom plates). The film is now curved along as well as across the top and bottom plates. Curvature along the plates arises from viscous drag forces on the channel sidewall boundaries. The maximum steady propagation velocity is unchanged, but can now also be associated with films meeting channel sidewalls tangentially, a situation which should be readily observable if the film is viewed from above the top plate. Observed from above, however, the film need not appear as an arc of a circle. Instead the film may be relatively straight along much of its length, with curvature pushed into boundary layers at the sidewalls

Reactions of Acid Orange 7 with Iron Nanoparticles in Aqueous Solutions

The physicochemical properties of two commercial dispersions of iron nanoparticles were studied, together with their behaviour in the room-temperature degradation in basic solutions of Acid Orange 7 (AO7), studied by UV-vis spectroscopy. In one dispersion (bare- RNIP), water was the solvent, and in the other (M-RNIP) a biopolymer (sodium aspartate) was added (RNIP standing for reactive nanoscale iron particles and M for modified). The features of iron nanoparticles (size, morphology, presence of oxidized phases) were studied both in the dispersions as such and in the corresponding dried powders. A protecting role of the biopolymer was observed, as well as changes in the properties with time (aging). With bare-RNIP, the fraction of Fe3O4 (magnetite) steadily increased with time at the expense of Fe0, eventually reaching 99%, and with M-RNIP, the Fe0 content was higher at any time than with bare RNIP: aging, however, brought about the formation of the Fe3+ compound FeOOH besides magnetite. As for AO7 degradation, a similar behaviour was observed with the two fresh dispersions: with M-RNIP, degradation was complete in a few minutes, and with fresh bare-RNIP, the same process was basically observed, though at a lower rate. In both cases, successive reactions were observed as a minor feature, for which an interpretation is advanced. Aging ofM-RNIP does not prevent the degradation reaction: aging in the absence of the polymer, instead, leads, after 6 months, to an entirely different process, consisting in the mere adsorption through the phenol group of AO7 onto the magnetite external layer of bare-RNIP particles. Further aging of bare-RNIP prevents also this phenomenon. The different behaviour of the two dispersions relates to the composition of iron nanoparticles. Reaction with water converts Fe0 into magnetite. When Fe0 is present and the thickness of the outer magnetite layer is moderate, AO7 degradation occurs. With a thick outer layer, only adsorption is possible, which does not take place on a fully oxidized surfac